1. Field of the Invention
The present invention relates to a measurement apparatus which measures the numerical aperture of an optical system to be measured, an exposure apparatus including the measurement apparatus, and a method of manufacturing a device using the exposure apparatus.
2. Description of the Related Art
An exposure apparatus for manufacturing devices such as semiconductor devices illuminates an original, on which a pattern is formed, with light to project the pattern of the original onto a substrate by a projection optical system. With this operation, the pattern of the original is transferred onto the photosensitive agent on the substrate. The resolution of the projection optical system depends on the numerical aperture (NA) of the projection optical system; the resolution improves as the numerical aperture increases. In view of this, the numerical aperture of the projection optical system is an important index indicating the performance of the projection optical system.
To calculate the numerical aperture of the projection optical system, one known method calculates a resolution RP of the projection optical system and computes the numerical aperture based on a relation RP=λ/NA (Japanese Patent Laid-Open No. 2002-5787). This method calculates the resolution RP by transferring various patterns having different line widths onto a substrate via the projection optical system, and measuring, by a measurement apparatus such as an SEM, the pattern thus formed on the substrate. Unfortunately, it is difficult to precisely calculate the numerical aperture because the resolution RP also depends on the properties of the photosensitive agent (photoresist) and the aberration of the projection optical system.